1. Field of the Invention
The present invention relates to an image forming apparatus and a conveyance control method.
2. Description of the Related Art
In an electrophotography image forming apparatus, an intermediate transfer belt to which an image formed by an image forming unit is transferred is expanded or contracted due to thermal expansion or contraction caused by the change in temperature.
In view of this, in order to form an image at an appropriate position on a recording sheet, it is necessary to perform image position correction for correcting the displacement in image transfer position or conveyance timing correction for correcting the paper conveyance timing in consideration of the expansion or contraction of the intermediate transfer belt.
In the technique disclosed in Japanese Patent Application Laid-open No. 2008-76534, based on the timing at which a first set of the displacement correction pattern is read, the timing of detecting second and subsequent sets of displacement correction patterns is decided. Therefore, even though the intermediate transfer belt is expanded or contracted, it is possible to perform the image position correction by certainly reading the displacement correction patterns of the second and subsequent sets.
Further, if a difference from a reference value of the time of detecting the displacement correction pattern is calculated and the conveyance timing correction is performed based on the calculated difference, the conveyance control of the recording sheet in consideration of the expansion and contraction of the intermediate transfer belt becomes possible.
In the conventional art as described above, the displacement correction pattern formed in color is used; however, from the viewpoint of the accuracy of the paper conveyance timing and the consumption of a developer, the conveyance timing correction using the displacement correction pattern formed in color may not be preferable.
The present invention has been made in view of the above circumstances, and an object is to provide an image forming apparatus and a conveyance control method, that can increase the accuracy of the conveyance control of the recording sheet while the extra consumption of a developer is reduced.